Vitamin B12/carbon nanotubes composites for highly efficient CO2 electroreduction with in situ shell-isolated nanoparticle-enhanced Raman spectroscopy

Electrocatalytic CO2 reduction reaction (ECO2RR) has attracted much attention for its ability to convert CO2 into valuable chemicals. However, it is still a challenge to achieve high Faradaic efficiency (FE) and high current density (j) in ECO2RR simultaneously. Vitamin B12 (VB12) has been considered as a novel and highly effective catalyst for electrocatalytic reduction of CO2 to produce CO in aqueous electrolyte, and carbon nanotubes (CNTs) have excellent conductivity. Herein, VB12/CNTs composites are deposited onto carbon paper by electrophoretic deposition. The prepared catalyst exhibits a high FE of CO (FECO) as 95.98% and the corresponding j of CO (j(CO)) is 40.85 mA cm(-2) at -0.86 V (vs. RHE) in 0.5 M KHCO3 electrolyte. Moreover, FECO is greater than 98% in the range from -2.0 V to -2.4 V (vs. Ag/Ag+), and the maximum FECO is as high as 99.29% with a j(CO) of 65.53 mA cm(-2) at -2.2 V (vs. Ag/Ag+) in ionic liquids (ILs) 1-butyl-3-methylimidazolium hexafluorophosphate (BmimPF(6)) electrolyte. In situ shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) demonstrates that the Co center of VB12 is the main ECO2RR active site. Density functional theory (DFT) calculations further indicate that the formation of COOH* is the rate-limiting step of the ECO2RR.